The prior art details numerous disclosures of flexible, motor vehicle bumpers that take advantage of the large energy absorbing capabilities of fluid systems. It is believed that such bumpers have restricted in their feasible production applications by two factors: lack of reliability and relatively great manufacturing costs.
Liquid filled bumpers and bumpers wherein a gas is encapsulated under pressure are prone to develop leaks. This is because the outer shells of such bumpers must be constructed from elastomeric materials that are subject to puncture or other sealing features during normal vehicle operation. In addition, known flexible bumpers including single or multiple, self-contained fluid chambers are difficult and costly to manufacture and can be secured to the vehicle structure to be protected only be relatively complex and expensive attachment means.
It is an object of this invention to provide a flexible, energy absorbing bumper adapted for use on a motor vehicle that takes advantage of the energy absorbing potential of fluid systems, but avoids the drawbacks to such bumpers encountered in the prior art and detailed above. More particularly, this invention provides a pneumatic bumper wherein air chambers are defined by a support and an elastomeric member that may be manufactured by conventional techniques that are compatible with high volume, low cost production. Small leaks in the structure defining these chambers do not affect bumper reliability because the air encapsulated therein normally is at atmospheric pressure and is pressurized during an impact at too great a rate to be significantly affected by such leaks. Furthermore, the bumper of this invention is reusable as the elastomeric member returns to its original shape following an impact thereupon. This return to its original shape by the elastomeric member occurs without giving rise to objectionable rebound forces.
This invention also provides a resilient pneumatic bumper in which the elements separating the chambers are so designed to create a preloading effect or a maximum buckling resistance. Also, the separator elements may provide controlled airflow from chamber to chamber upon impact of the bumper shell.